(a) Field of the Invention
The present invention relates to a composite film which has excellent punching capability and is useful as a bonding element for semiconductor packaging.
(b) Description of Related Art
In semiconductor packaging, a bonding element which is a composite film produced by coating one or both sides of a base film with adhesives is used for bonding chips to lead frames to form LOC (lead on chip) or COL (chip on lead) structures or window-tub structures, or for bonding inner leads to heat spreaders to form composite lead frames with heat sinks attached. The bonding element is generally applied to the lead frames by punching out the bonding element from the composite film over the lead frames and pressing the bonding elements to required parts of the lead frames. However, the yield rate of the resulting lead frames with composite film attached is low since flashes are frequently formed at the punched edges of the composite film.